Alcohol's Effects on Female Reproductive Function

Article excerpt

Mild-to-moderate alcohol use has numerous negative consequences for female reproductive function. Animal studies have shown that alcohol consumption disrupts female puberty, and drinking during this period also may affect growth and bone health. Beyond puberty, alcohol has been found to disrupt normal menstrual cycling in female humans and animals and to affect hormonal levels in postmenopausal women. Research has explored the mechanisms of these effects and the implications of these effects for bone health. KEY WORDS: reproductive effects of AODU (alcohol and other drug use); reproductive function; female; hypothalamic-pituitary-gonadal axis; hormones; puberty; postmenopause; menstrual cycle; osteoporosis

Mild-to-moderate alcohol use affects female reproductive function at several stages of life. It has been shown to have a detrimental effect on puberty, to disrupt normal menstrual cycling and reproductive function, and to alter hormonal levels in postmenopausal women. In addition, alcohol use can have implications for bone health. Before examining alcohol's effect on female reproduction and the potential mechanisms of these effects, this article reviews normal female reproduction, including puberty, the normal female cycle, and hormonal changes in postmenopausal females.

OVERVIEW OF THE FEMALE REPRODUCTIVE SYSTEM

The female reproductive system includes three basic components: a brain region called the hypothalamus; the pituitary gland, located at the base of the brain; and the ovaries (Molitch 1995). These three components together make up the female hypothalamic-pituitary-gonadal (HPG) axis. This system is described in figure 1.

Normal Mammalian Puberty

Puberty is the dramatic awakening of the HPG axis, resulting in marked alterations in hormonal activity (especially the pituitary and gonadal hormones), physiologic processes (such as reproduction and growth), and behavior. It is generally accepted that this results from the activation of the hypothalamic secretion of luteinizing hormone-releasing hormone (LHRH), which in turn stimulates the pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which leads to maturation and function of the ovaries (Mauras et al. 1996; Veldhuis 1996; Apter 1997). Because, like most hormones, LHRH is secreted episodically in pulses, rather than continuously, puberty has been viewed as an awakening of the LHRH pulse generator. Puberty is marked not only by the activation of reproductive processes but also by a growth spurt. The accompanying hormonal changes are depicted in figure 2.

The increased HPG activity and increased growth hormone (GH) secretion that occur during puberty are functionally interrelated, in that a variety of human and animal data have shown that the form of estrogen known as estradiol markedly stimulates the secretion of GH (Mauras et al. 1996). Moreover, the growth-stimulating hormone insulin-like growth factor 1 (IGF-I) can stimulate LHRH (Hiney et al. 1998). Thus, the HPG axis is activated, leading to both sexual maturation and a growth spurt, via estrogen's stimulatory effects on the GH-IGF axis.

Pubertal development is influenced not only by HPG and GH-IGF activities but also by the opioid pathway. Endogenous opioid peptides (EOPs) are natural chemicals found in the body that act like opiates. There are three major EOPs, products of three separate genes. The major peptide in the female reproductive system is beta-endorphin, which is made in the hypothalamus as well as throughout the brain and in the pituitary Hypothalamic bera-endorphin restrains the secretion of hypothalamic LHRH and inhibits the HPG axis. Compounds such as naloxone and naltrexone that block the effect of beta-endorphin are known as opiate antagonists. These compounds have been widely used to study the mechanisms of opioid inhibition of the HPG axis. In early puberty, naloxone administration does not change LH levels, indicating that normally during this time, little opioid inhibition of the HPG axis occurs (Petraglia et al. …